The potential reserves of liquid hydrocarbons contained in subterranean carbonaceous deposits are known to be very substantial and form a large portion of the known energy reserves in the world. In fact, the potential reserves of liquid hydrocarbons to be derived from oil shale greatly exceed the known reserves of liquid hydrocarbons to be derived from petroleum. As a result of the increasing demand for light hydrocarbon fractions, there is much current interest in economical methods for recovering liquid hydrocarbons from oil shale on commercial scales.
It has long been known that oil may be extracted by heat from various extensive deposits of porous minerals known by their generic term oil shale, which are permeated by a complex organic material called "kerogen". Upon application of heat, the kerogen is converted to a complex mixture of hydrocarbons and hydrocarbon derivatives which may be recovered from a retort as a liquid shale oil product.
Eastern shales are known to contain an equal proportion of organic carbon as the western shales. However, upon retorting only 30% of this carbon is converted to oil. This conversion is less than half of the conversion achieved by retorting western shale. To clarify this fact, consider two shale oil samples containing 13.6% organic carbon. Retorting the western shale would reduce this carbon to about 4%. On the other hand, retorting eastern shale would reduce this carbon to only about 10%. Thus, any technique that may be used to improve this conversion as measured by enhancement in oil yield will be highly advantageous particularly when applied to eastern shale.
Accordingly, the present invention provides a process to enhance the yield of hydrocarbon fluids in the retorting of oil shale.